Phys.org September 6, 2024
Deposition of wildfire smoke on snow contributes to its darkening and accelerated snowmelt. Recent field studies have identified dark brown carbon (d-BrC) to contribute 50–75% of shortwave absorption in wildfire smoke. d-BrC is a distinct class of water-insoluble, light-absorbing organic carbon that co-exists in abundance with black carbon (BC) in snow across the world. However, the importance of d-BrC as a snow warming agent relative to BC remains unexplored. Researchers at Washington University in St. Louis addressed this gap using aerosol-snow radiative transfer calculations on datasets from laboratory and field measurement and showed that d-BrC increased the annual mean snow radiative forcing between 0.6 and 17.9 W m−2, corresponding to different wildfire smoke deposition scenarios. This is a 1.6 to 2.1-fold enhancement when compared with BC-only deposition on snow. According to the researchers their study suggests that d-BrC is an important contributor to snowmelt in midlatitude glaciers, where ~40% of the world’s glacier surface area resides… read more. Open Access TECHNICAL ARTICLEÂ
Daily mean radiative forcing over the span of a year. Credit: npj Climate and Atmospheric Science volume 7, Article number: 200 (2024)